Generally, a fluid cutoff device is configured to prevent water contamination, when sludge is removed from a riverbed using a suction-type dredge. An example of the dredge will be described with reference to FIGS. 1 and 2. As shown in the drawings, the dredge includes a hydraulic pump 2, a vacuum generating unit 3, and a height adjustable ladder 4 that are provided at predetermined positions on a dredger. Further, the dredge includes a suction pipe 5 which is supported by the ladder 4 to vary the depth of the suction pipe 5, and a suction head 6 which is mounted to a lower end of the suction pipe 5. The position and angle of the ladder 4 are adjusted so that the suction head 6 comes into contact with a riverbed 7. A hydraulic hose is coupled to the suction head 6, so that hydraulic pressure is transmitted from the hydraulic pump 2 to the suction head 6. Further, a flow restriction means, namely, a fluid cutoff device is provided at a position around the suction head 6 to vertically move along the suction pipe 5 of the suction-type dredge.
The fluid cutoff device includes a cover 10, a skirt 11, a heavy substance 12, and a rope guide means 20. The cover 10 covers a portion around the suction head 6, and has at a center thereof a pipe guide hole 16 to receive and guide the suction pipe 5. The skirt 11 is mounted to a lower end of the cover 10 and is made of a flexible material. The heavy substance 12 is provided on a lower end of the skirt 11. The rope guide means 20 is integrally provided on an upper surface of the cover 10 to move the cover 10 up and down.
The rope guide means 20 is constructed to guide a rope 21 using a rope drawing motor 22 which is installed at a predetermined position on the dredger, thus winding or unwinding the rope 21.
As shown in FIG. 2, it is preferable that reinforcing ribs 13 be radially provided on the cover 10 at regular intervals, thus increasing the durability of the cover 10. Further, holes 14 are formed on the cover 10 to decrease pressure which is generated during the vertical movement of the cover 10. The cover 10 also includes a ring-shaped support frame 15 to form the pipe guide hole 16.
The conventional cutoff device performs a function of decreasing pressure during the initial downward movement of the cover in dredging work. However, the cutoff device has a problem in that contaminants generated during the dredging work leak out, thus causing environmental contamination.